Technologies


 

COMC concentrates itself on the development of the automatic meteo-oceanographic measuring systems as well as study on the numerical modeling. In order to meet the requirement of data applications, real-time data transmission function is designed in all measuring systems. In order to improve the forecast results, the data assimilation technology is applied. Currently, six operational systems have been developed and are under operation. They are introduced below.

 

 

COMC Data Buoy

資料浮標細部sA new type of data buoy was designed and developed by COMC in order to monitor the oceanographic and meteorological data in the sea. To consider the operational requirements of low cost of manufacture and refurbishment, lightweight, land and sea transportability, wave-following characteristics, and reliability, the buoy was designed as a 2.5 meters discus-shaped foam buoy to be easily and safely handled without special equipment or procedures. 

The buoy hull, which has a 5083-alloy aluminum deck diameter of 2.5 meters, consists of twelve foam flotation compartments surrounding a center payload compartment shell (0.54-meter high and 0.6-meter in diameter).  A three-legged 304-stainless steel mast bolts to pads on the buoy hull's deck.  A three-legged 304-stainless steel mooring bridle beneath the buoy provides additional stability.  Solar panels, a marker light, a radar reflector, antenna and sensors mount to the mast.  The two anemometers are mounted on the mast at approximately 3 meters above the sea surface. Sea and air temperature sensors are installed 0.4 meters below and 2 meters above the surface water, respectively. Barometric pressure measurement is taken 2 meters above the sea level. Internally mounted electronics and batteries are installed on a removable aluminum rack in the central compartment. The electronics payload system is an automated, self-timed system that processes the data into required forms and transmits the formatted codes through the radio telemetry. The buoy's payloads and light are typically powered from secondary batteries with solar charging and primary-battery backup.

The choice of mooring design used usually depends on its intended deployment location, water depth and measurement requirement. In shallow coastal waters the buoy could be towed by ship at low speed and deployed on all-chain moorings.  However, it should be carried on deck and deployed overboard by crane in the deep-water deployment. Due to limited reserve buoyancy, the buoy in deeper water requires combination moorings of chain and a segment of stainless steel cable in the middle part of mooring instead of all-chain moorings. A buoy's position is then traced by a GPS and sent to COMC to inspect the buoy adrift from its moorings.

Before launching the buoy, there are some procedures to test the performances such as: test of the water/humidity air resistance, calibration of meteorological sensors, calibration of accelerometer and inclinometer, calibration of compass heading, test of neutral frequency of the buoy hull, system run in, and test of short term field operation.

Currently, there are 9 COMC data buoy located in the coastal ocean around Taiwan and 1 COMC data buoy located at Gagua Ridge where the water depth is 4800 m and the distance is 250 km away from the eastern coast of Taiwan. They are all long-time operation and with real-time data transmission function. These data buoy are supported by Central Weather Bureau, Water Resources Agency and Tourist Bureau of Taiwan.

                                                                                                               

Download: COMC Data Buoy Introduction (PDF file)

 

Numerical Model Forecasting

COMC is developing numerical wave and current models. Large scale NOAA WAVEWATCH III (NWW3) wave model is nested with small scale SWAN model in order to forecast ocean wave field. COMC develop them to operational models. In addition, POM model is studied to simulate current field. To improve model accuracy, the data assimilation technique is applied. It is to integrate field data from the existing operational monitoring network with the numerical models.

NWW3 model:

WAVEWATCH III (Tolman 1997, 1999a) is a third generation wave model developed at NOAA/NCEP in the spirit of the WAM model (WAMDIG 1988, Komen et al. 1994). It is a further development of the model WAVEWATCH I, as developed at Delft University of Technology (Tolman 1989, 1991) and WAVEWATCH II, developed at NASA, Goddard Space Flight Center (e.g., Tolman 1992). It nevertheless differs from its predecessors on all important points; the governing equations, the models structure, numerical methods and physical parameterizations.

WAVEWATCH III solves the spectral action density balance equation for wavenumber-direction spectra. The implicit assumption of these equations is that the medium (depth and current) as well as the wave field vary on time and space scales that are much larger than the corresponding scales of a single wave. Furthermore, the physics included in the model do not cover conditions where the waves are severely depth-limited. This implies that the model can generally by applied on spatial scales (grid increments) larger than 1 to 10 km, and outside the surf zone.

SWAN model:

The SWAN (Simulating WAves Nearshore) model is a spectral wave model developed at the Delft University of Technology, The Netherlands.  SWAN models the energy contained in waves as they travel over the ocean surface towards the shore.  In the model, waves change height, shape and direction as a result of wind, white capping, wave breaking, energy transfer between waves, and variations in the ocean floor and currents.  Initial wave conditions, including wave height, wave direction and wave period (time it takes for one wavelength to pass a fixed point), are entered into the model, and the model computes changes to the input parameters as the waves move toward shore.  Model results are computed on a 500-m by 500-m grid (or smaller) for the area of research.  Model output information (wave height, wave direction, and wave velocity) is produced for each cell in the model grid, and can be displayed in a map view to simplify visualization of changes in waves over the study area.

 

POM model:

The Princeton Ocean Model (POM) is used to simulate temperature, current and salinity conditions along coastal areas where topographical slopes are fairly gradual, such as those in semi-enclosed seas, harbors, bays and estuaries. Because it describes both ocean dynamics and thermodynamics, the POM model is used to study a broad range of coastal problems. In the area of environmental research, it is used to predict the environmental quality of coastal waters, model the effect of oil spills and assist in other coastal forecasting.

 

Following image is an animation of significant wave height (SWH) around Taiwan coast during a typhoon. It is simulated by nesting NWW3 and SWAN models.

 

Homepage of SWH forecasted by the operational wave models. 

 

 

COMC Patent Portfolio

專利證書aCOMC owns 4 patents up to 2005. The patent of COMC data buoy (Patent No. 087358) belongs to the category of new invention. It covers the hardware of buoy system itself as well as the relevant methods and software.

List of COMC patents

˙    Concept and method of Meteo-Oceanographic data measurement by buoy

˙    Instrument of wave run-up measurement

˙    Real-time GPS drifting buoy

˙    Ship-mount instrument on Meteo-Oceanographic data measurement